Mrs Fletcher’s comments were supported by Paul McKeever, the chairman of the Police Federation of England and Wales, which represents rank and file officers.

Mr McKeever, a former Metropolitan Police officer, told said: “I think this is the best opportunity over the past 25 years to bring the killers to justice. I would expect the Home Office and the Foreign Office to be working towards that end.”

Andrew Mitchell, the international development secretary, promised that every effort would be made to bring WPc Fletcher’s killers to justice.

“There is no question whatsoever that, following a free Libya under the control of the National Transitional Council, that is an issue the Government will want to pursue with the new Libyan authorities,” he said.

“I am reasonably confident that a judicial process designed to bring that heinous crime to court would indeed take place.” The Daily Telegraph disclosed in October 2009 that a report by an independent prosecutor informed the Met and the Crown Prosecution Service in April 2007 that they had sufficient evidence to charge two Libyans — Matouk Mohammed Matouk and Abdulgader Mohammed Baghdadi — with conspiracy to cause death. The 140-page report also named a man suspected of firing the fatal shot, but said there was not enough evidence to bring any murder charges.

Scotland Yard detectives were allowed into Tripoli in July last year for the first time in four years after heavy lobbying by David Cameron in the months after he became Prime Minister. They have not returned since last August.

A Scotland Yard spokesman said: “The case remains open and we remain committed to identifying those responsible for killing WPc Yvonne Fletcher.”

In March, rebels captured a Gaddafi supporter linked to the shooting of WPc Fletcher. Omar Ahmed Sodani was working at the embassy in St James’s Square at the time. He insisted he did not carry out the shooting.